ENGR00257947 mtd: use memcpy to replace the memcpy_fromio

During the read of NOR, the kernel actually calls the inline_map_copy_from()
to read the data out. And inline_map_copy_from() will use the memcpy_fromio()
to do the real job.

The memcpy_fromio macro maps _memcpy_fromio() in the current code.
But the _memcpy_fromio() will use readb() to do the copy work one byte
by one byte. This makes the read performance of NOR very slow(about 2~3MB/s).

A similiar discussion could be found in:
http://lists.infradead.org/pipermail/linux-arm-kernel/2009-November/003860.html

This patch replace the memcpy_fromio with memcpy which is optimized by the
kernel.

The following is the result from mtd_speedtest with M29W256GL7AN6E:
=================================================
mtd_speedtest: MTD device: 2
mtd_speedtest: not NAND flash, assume page size is 512 bytes.
mtd_speedtest: MTD device size 4194304, eraseblock size 131072, page size 512,
		count of eraseblocks 32, pages per eraseblock 256, OOB size 0
mtd_speedtest: testing eraseblock write speed
mtd_speedtest: eraseblock write speed is 845 KiB/s
mtd_speedtest: testing eraseblock read speed
mtd_speedtest: eraseblock read speed is 19504 KiB/s
mtd_speedtest: testing page write speed
mtd_speedtest: page write speed is 845 KiB/s
mtd_speedtest: testing page read speed
mtd_speedtest: page read speed is 19140 KiB/s
mtd_speedtest: testing 2 page write speed
mtd_speedtest: 2 page write speed is 846 KiB/s
mtd_speedtest: testing 2 page read speed
mtd_speedtest: 2 page read speed is 19320 KiB/s
mtd_speedtest: Testing erase speed
mtd_speedtest: erase speed is 233 KiB/s
mtd_speedtest: Testing 2x multi-block erase speed
mtd_speedtest: 2x multi-block erase speed is 225 KiB/s
mtd_speedtest: Testing 4x multi-block erase speed
mtd_speedtest: 4x multi-block erase speed is 224 KiB/s
mtd_speedtest: Testing 8x multi-block erase speed
mtd_speedtest: 8x multi-block erase speed is 225 KiB/s
mtd_speedtest: Testing 16x multi-block erase speed
mtd_speedtest: 16x multi-block erase speed is 225 KiB/s
mtd_speedtest: Testing 32x multi-block erase speed
mtd_speedtest: 32x multi-block erase speed is 225 KiB/s
mtd_speedtest: Testing 64x multi-block erase speed
mtd_speedtest: 64x multi-block erase speed is 224 KiB/s
mtd_speedtest: finished
=================================================

Signed-off-by: Huang Shijie <b32955@freescale.com>

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